Check this out:
Windows Live ID Team has published on the web the SDK that lets you liveID (or "passport")-enable your applications!
There are even code samples in six different languages: C#, Java, PHP, Python, Ruby e Perl! You can download them from http://go.microsoft.com/fwlink/?LinkId=91761
Wow! Having time, it would be cool to write a WordPress plugin using Passport authentication to authenticate/identify users that want to comment… mumble mumble….. 🙂
More info at the Live ID starting Page: http://dev.live.com/blogs/liveid/archive/2006/05/18/8.aspx